I dunno, just based on how much studios believe they need to deliver in a AAA title. You seem like you’re craving a simpler experience than the enormous budget and revenue expectations dictate will get created.
The ideal sequel would be "Civ 1, with new graphics and better automation". Then iterate on that every few years.
I'm not sure the civ guys can come up with something to compete with it. The recent games were so bloated and everything dragged on to the to point you'd just lose interest mid game, or quit before an inevitable victory/loss in the late game.
Also I'm not sure what you could do to improve Polytopia to make it a better game, except adding multiplayer team games.
Just because new players didn't know how to scout and/or that artillery does collateral damage to stacks...